1. Field of the Invention
This invention relates generally to electronic devices, such as a cordless telephone. More particularly, it relates to any electronic device which reduces standby power to minimize power usage based on selective criteria.
2. Background of Related Art
A modern home typically contains many electronic devices, e.g., home entertainment equipment such as televisions, video cassette recorders (VCRs), digital video disk (DVD) players, compact disk (CD) players, cordless telephones, etc.
As a particular example for the purpose of explanation, a modern home may contain a cordless telephone. A cordless telephone typically includes a cordless, remote handset, and an associated base unit or station. Typically, the base unit is powered by conventional AC current from a household electrical outlet and the remote handset operates using battery power. To recharge the battery in the remote handset, the remote handset is typically inserted into a cradle in the base station and recharging power (e.g., trickle power) is applied to the battery of the remote handset using the AC current of the base unit. Most users of cordless telephones, however, desire to keep the remote handset away from the base unit for extended periods of time, e.g., so that they may carry the remote handset with them as they move about their residence or other locale.
When removed from the base unit, it is typically desirable for the user to have the remote handset ring as soon as possible or feasible after a ring signal is detected on the telephone line by the base unit. To accomplish this, the remote handset is required to be in an ON mode having continuous communication with the base unit. In this way, the remote handset can detect and receive the incoming ring signal as soon as it is first transmitted by the base unit.
Another technique to conserve some battery power and thereby have the potential to extend the operational life of the remote handset between charges is to periodically power-down and power-up the remote handset. In this STANDBY mode, the remote handset is periodically powered-up at desired intervals to receive a status update from the base unit, then if not required to perform a particular task the remote handset will power back down. In this way, the remote handset will periodically enter the low power STANDBY mode and turn on the RF front end in a receive only mode to check if, e.g., an incoming call is being received by the base unit. If, e.g., an incoming ring signal is detected in the status update, the remote handset will fully power up and enter an ON mode. The remote handset will also enter the ON mode in response to the activation of a button or appropriate sequence of buttons on the remote handset or base unit.
Thus, in the typical STANDBY mode, a remote handset must periodically communicate with the base unit, e.g. approximately every one (1) second or so, to receive a ring signal relating to an incoming telephone call, at least within a reasonable proximity to when the ring signal was originally detected on the telephone line into the base unit. Moreover, the periodic communication helps the remote handset to maintain an aligned communication link with the base unit.
Much of the battery power in a typical remote handset is utilized by a radio frequency (RF) front end. The RF front end provides the radio communications between the base unit and the remote handset. When the remote handset is in its ON mode, the RF front end will require a significant power drain from the battery in the remote handset, causing perhaps the shortest possible operational life between charges. Moreover, even though the STANDBY mode has the potential to extend the operational life of the remote handset significantly, the periodic powering of the RF front end still utilizes a significant amount of battery power.
FIG. 1 illustrates a conventional single handset, cordless telephone capable of answering an incoming call on a telephone line.
In particular, in FIG. 1, a cordless telephone 11 has a base unit 13 connected to a telephone company central office 15 via a telephone line 17. The base unit 13 is connected to a conventional household AC power outlet 19 for providing power to the base unit 13.
The base unit 13 further includes a base unit antenna 21 for communication with a remote handset antenna 23 on a remote handset 25. The remote handset 25 includes a battery 27 for providing power to the remote handset 25. The battery 27 is rechargeable by the conventional household AC power outlet 19 by placing the remote handset 25, e.g., into an appropriate cradle in the base unit 13.
When a ring signal is detected by the base unit 13 over the telephone line 17, the ring signal status is transmitted over the base unit antenna 21 to the handset antenna 23 for detection by the remote handset 25 to cause the remote handset 25 to ring and thereby indicate the presence of an incoming telephone call to the user.
In an ON mode, the remote handset 25 is in continuous communication with the base unit 13, e.g., actively transmitting and/or receiving data and/or control information with the base unit 13. In a STANDBY mode, the communications are periodic and receive only. In an OFF mode, the remote handset 25 is not in communications with the base unit 13 and is not able to detect and/or receive a ring signal from the base unit 13.
In any event, the user must recharge the battery 27 in the remote handset 25 by returning the remote handset 25 to the cradle in the base unit 13 to allow the battery 27 to be recharged by the AC power from the outlet 19. This recharging requirement necessarily requires connection of the remote handset to the base unit, and thus deprives the user of much of the flexibility and utility of a cordless telephone, at least while it is recharging.
Accordingly, there exists a need for apparatus and techniques for minimizing power usage of home electronic equipment such as a cordless telephone, to either minimize power usage in general and, for battery powered devices, to maximize the operational time between charges.